Field of the Invention
This invention relates to a trench shoring assembly and, in particular, to a trench shoring assembly known as a trench box.
Trench boxes are typically used in excavation work when pipe is being laid, such as sewer or drain conduit. Basically, a trench box consists of two walls spaced apart a fixed distance from each other by a plurality of spreader devices affixed to and perpendicular to each side wall. Assembled trench boxes are positioned in an excavated hole or trench and pipe is laid within the trench box and after each length of pipe is laid the trench box is moved along the trench for laying the next length of pipe. The side walls of the trench box keep the excavation free from earth which has a tendency to fall or cave into the excavated hole or trench before and during the laying of the pipe.
Prior trench boxes are typically rigid. That is, the spreader pipes rigidly interconnect the spreader walls when in use. Rigid trench boxes often stick in the ground due to the side wall pressures from caved in earth during normal trench box lifting-out procedures. A rigid trench box is also difficult to .[.position .]. .Iadd.position .Iaddend.within an excavated trench.
Some trench shoring devices allow for complete pivotal movement between the spreader pipes and the side walls while the trench box is being positioned within the trench but, upon being positioned within the trench, the spreader pipes and the side walls are then rigidly attached or made rigid.
In accordance with the subject invention, there is provided a trench shoring assembly including a pair of spaced wall means for vertical disposition within a trench and connecting means interconnecting the spaced wall means for allowing limited pivotal movement between the spaced wall means.
The present invention, therefore, provides a trench box whose side walls can move to a limited extent vertically relative to one another. That is, one of the side walls may be raised in relation to the other. In this way, the trench box will lift out of the hole with much less effort than a rigid trench box, and also the trench box will not stick in the ground due to the side wall dirt pressures since, if one of the side walls become stuck due to side wall pressures, the opposite side wall can be moved upward to "walk" the trench box out of the trench.